It is proposed that we continue to develop highly selective procedures suitable for synthesizing olefins, especially trisubstituted olefins of terpenoid origin based on (a) the controlled carbometallation promoted by early transition metals, i.e., titanium, zirconium and halfnium and (b) the cross coupling catalyzed by Group VIII metals, e.g., nickel and palladium. Some of the specific plans are as follows: 1. investigation of the Zr- or Ti-catalyzed carbometallation of hetero-substituted acetylenes, 2. application of the above reaction to the synthesis of silicon-substituted acyclic allylic halides having terpenoid carbon skeletons and investigation of their cyclization reactions as a potential, regioselective route to cyclic terpenes, e.g., germacrenes and humulene, 3. investigation of the Zr- or Ti-catalyzed cyclic carbometallation of internal acetylenes and its application to stereoselective syntheses of steroidal compounds, e.g., vitamin D, 4. development of Pd- or Ni-catalyzed cross-coupling reactions for the synthesis of skipped dienes, enynes and allylarenes and their application to selective syntheses of terpenes, such as alpha-farnesene, vitamine K, and other natural products.